1. Field of the Invention
Aspects of the present invention relate to a battery management system, method, and device. More particularly, aspects of the present invention relate to a method of battery management that can be used on a vehicle that uses electrical energy, a battery management system using the same, and a device to estimate an internal impedance of a battery.
2. Description of the Related Art
Vehicles that use an internal combustion engine, which uses gasoline or diesel oil as fuel, cause environmental pollution, such as air pollution. In order to reduce the amount of environmental pollution, efforts have been made to develop electric vehicles and hybrid vehicles.
An electric vehicle uses a battery engine that is powered by an electrical energy output of a battery. The electric vehicle uses the battery, in which a plurality of rechargeable battery cells are formed into one pack, as a main power source. By using an electric power source and battery engine rather than an internal combustion engine, the electric vehicle does not output exhaust gases and other environmental pollutants.
A hybrid vehicle is a cross between a vehicle using an internal combustion engine and an electric vehicle. The hybrid vehicle uses two or more kinds of power sources. For example, a hybrid vehicle may use both an internal combustion engine and a battery engine. Another type of hybrid vehicle uses both an internal combustion engine and fuel cells that directly obtain electrical energy by a chemical reaction when supplied with reactants such as hydrogen and oxygen. A third type of hybrid car uses a battery engine and fuel cells.
The performance of an electric or hybrid vehicle using electrical energy to power a battery engine is directly affected by the efficiency of the battery. For the battery to operate efficiently, each battery cell needs to have high performance. This requires a battery management system which is capable of efficiently managing the charging and discharging of the battery cells by measuring a voltage of each battery cell, battery voltage, and battery current.
To efficiently charge, discharge, and manage a battery, accurate and timely data on the internal impedance of the battery is required. Accurate internal impedance data is difficult to acquire because the internal impedance of the battery changes according to external and internal conditions, such as temperature, SOC (State of Charge: available output capacity relative to a full charge), battery charge or discharge current, and SOH (State of Health: present performance of the battery, which decreases over its lifetime). Because of the large number of variables required to determine the internal impedance of the battery, it would be very difficult to create an accurate table listing the internal impedance of the battery under all required real world conditions.
The information disclosed in this Background section is only to provide an understanding of the background of the invention and not to establish the current level of the art. The Background section therefore may contain information that is not part of the prior art and is not known to a person of ordinary skill in the art.